1. Field of the Invention
This invention relates to a device for correcting the distortion of an image projected on a projection screen by a projector when the optical axis of the projection lens of the projector is not perpendicular to the projection screen. The present invention relates more specifically to a device provided in a projector such as a slide projector or an overhead projector for correcting the distortion of an image obliquely projected on a projection screen supported on a wall or the like.
2. Description of the Prior Art
When an image is projected on a screen supported on a wall or the like by a projector such as a slide projector or an over-head projector, the image is distorted if the optical axis of the projection lens of the projector is not perpendicular to the plane of the projection screen. For instance, if the image is projected on a screen located at a level higher than that of the projector, as often occurs particularly in case of over-head projectors, the upper part of the image is enlarged in comparison with the lower part. Thus, the image projected on the screen is apt to be distorted owing to the difference in level between the projector and the screen.